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 ###Instrução: Qual é a duração média (em meses) dos projetos de inovação militar para cada categoria?
 ###Tabelas: 
CREATE TABLE if not exists military_innovation (year INT, category TEXT, project TEXT, duration INT); INSERT INTO military_innovation (year, category, project, duration) VALUES (2015, 'Electronics', 'Stealth Technology Development', 36); INSERT INTO military_innovation (year, category, project, duration) VALUES (2016, 'Electronics', 'Stealth Technology Development', 42); INSERT INTO military_innovation (year, category, project, duration) VALUES (2015, 'Electronics', 'Artificial Intelligence Development', 24); INSERT INTO military_innovation (year, category, project, duration) VALUES (2016, 'Electronics', 'Artificial Intelligence Development', 30); INSERT INTO military_innovation (year, category, project, duration) VALUES (2015, 'Armament', 'Laser Weapon Development', 48); INSERT INTO military_innovation (year, category, project, duration) VALUES (2016, 'Armament', 'Laser Weapon Development', 54); INSERT INTO military_innovation (year, category, project, duration) VALUES (2015, 'Armament', 'Smart Ammunition Development', 30); INSERT INTO military_innovation (year, category, project, duration) VALUES (2016, 'Armament', 'Smart Ammunition Development', 36);
SELECT category, AVG(duration / 12.0) as avg_duration_months FROM military_innovation GROUP BY category;